U.S. patent number 5,478,686 [Application Number 08/037,185] was granted by the patent office on 1995-12-26 for fixable toner with a modified bisphenolic polyester resin.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Shinji Doi, Yasuhide Goseki, Yusuke Karami, Takashige Kasuya, Hiroaki Kawakami, Kiyoko Maeda, Satoshi Matsunaga, Masuo Yamazaki.
United States Patent |
5,478,686 |
Kawakami , et al. |
December 26, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Fixable toner with a modified bisphenolic polyester resin
Abstract
A heat fixable toner comprises a binder resin and a release
agent. The binder resin comprises a polyester resin, and the
release agent comprises a graft-modified polyolefin.
Inventors: |
Kawakami; Hiroaki (Yokohama,
JP), Karami; Yusuke (Yokohama, JP), Doi;
Shinji (Kawasaki, JP), Matsunaga; Satoshi (Tokyo,
JP), Goseki; Yasuhide (Yokohama, JP),
Kasuya; Takashige (Yokohama, JP), Yamazaki; Masuo
(Kawasaki, JP), Maeda; Kiyoko (Yokosuka,
JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
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Family
ID: |
27334748 |
Appl.
No.: |
08/037,185 |
Filed: |
March 25, 1993 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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593812 |
Oct 5, 1990 |
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Foreign Application Priority Data
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Oct 5, 1989 [JP] |
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1-258684 |
Nov 14, 1989 [JP] |
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1-294036 |
Dec 29, 1989 [JP] |
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1-343251 |
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Current U.S.
Class: |
430/109.4;
430/108.8; 430/111.4 |
Current CPC
Class: |
G03G
9/08704 (20130101); G03G 9/08755 (20130101); G03G
9/08782 (20130101); G03G 9/08786 (20130101); G03G
9/08795 (20130101) |
Current International
Class: |
G03G
9/087 (20060101); G03G 009/083 () |
Field of
Search: |
;430/110,106.6,107,109,137 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0104805 |
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Apr 1984 |
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EP |
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0183566 |
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Jun 1986 |
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EP |
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0195604 |
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Sep 1986 |
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EP |
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60-004947 |
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Jan 1985 |
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JP |
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60-067958 |
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Apr 1985 |
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JP |
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62-265670 |
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Nov 1987 |
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JP |
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1-015755 |
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Jan 1989 |
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JP |
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2082788 |
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Mar 1982 |
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GB |
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Primary Examiner: McCamish; Marion E.
Assistant Examiner: Weiner; Laura
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Parent Case Text
This application is a continuation of application Ser. No.
07/593,812 filed Oct. 5, 1990, now abandoned.
Claims
We claim:
1. A heat fixable toner comprising a binder resin and a
graft-modified polyolefin as a release agent, wherein said binder
resin comprises a bisphenolic polyester resin, said polyester resin
being obtained by co-condensation of an acid component containing
aromatic dicarboxylic acids in amounts of at least 30 mole % based
on the total of said acid component and an alcohol component
containing etherified bisphenols in amounts of at least 80 mole %
based on the total of said alcohol component and having the
properties that the melt viscosity .eta.' measured with an overhead
flow tester is from 10.sup.3 to 10.sup.6 poise at a temperature
within the temperature range of from 80.degree. C. to 120.degree.
C. and an absolute value of the inclination of a graph is not more
than 0.50 ln (poise)/.degree.C. when the natural logarithms
ln.eta.' of the melt viscosity at 80.degree. C. and 120.degree. C.
are plotted with respect to the temperatures; and
said graft-modified polyolefin comprises an .alpha.-olefin polymer
graft-modified with a grafting agent of from 0.1 to 100 parts by
weight based on 100 parts by weight of the .alpha.-olefin polymer,
wherein said grafting agent comprises from 20 to 80% by weight of a
styrenic monomer and from 80 to 20% by weight of at least one
monomer selected from the group consisting of methacrylic monomer,
acrylic monomer, maleic monomer, fumaric monomer, itaconic monomer
and citraconic monomer.
2. A heat fixable toner according to claim 1, wherein said binder
resin comprises a mixture of a linear polyester resin having an
acid value of less than 5 mg.KOH/g and a non-linear polyester resin
having an acid value of from 5 to 60 mg.KOH/g, and said
graft-modified polyolefin comprises a graft-modified polyolefin
having a low melting point.
3. A heat fixable toner according to claim 2, wherein said
graft-modified polyolefin has a melting point of from 60.degree. to
120.degree. C.
4. A heat fixable toner according to claim 2, wherein said
graft-modified polyolefin has a melting point of from 60.degree. to
100.degree. C.
5. A heat fixable toner according to claim 1, wherein:
said bisphenolic polyester resin comprises a polyester resin
obtained by co-condensation polymerization of an etherified
bisphenol with a carboxylic acid or its derivative, including a
carboxylic acid with two or more carboxylic groups, an anhydride
thereof or a lower alkyl ester thereof and;
said graft-modified polyolefin has a melt viscosity of from 1 to
250 cps (centipoise) at 160.degree. C. and is contained in an
amount of from 0.1 to 20% by weight based on the weight of the
binder resin.
6. A heat fixable toner according to claim 1, including a coloring
agent and wherein:
said bisphenolic polyester resin comprises a polyester resin having
an acid value of from 5 to 60, formed of:
(A) an etherified bisphenol;
(B) not less than 30 mol % of an aromatic dicarboxylic acid, in all
acid components;
(C) 5 to 40% by weight of an alkenyl-substituted dicarboxylic acid,
an alkyl-substituted dicarboxylic acid or mixtures thereof, based
on the total amount of acids; and
(D) a polycarboxylic acid with three or more carboxylic groups, a
polyol with three or more hydroxy groups, or mixtures thereof;
an organic metal compound comprising a metal of valence of two or
more is present in an amount of from 0.2 to 6% by weight based on
the weight of the binder resin;
said graft-modified polyolefin has a melt viscosity of from 1 to
250 cps (centipoise) at 160.degree. C. and is present in an amount
of from 0.1 to 20% by weight based on the weight of the binder
resin; and
said toner has a melt viscosity .eta.' measured with an overhead
flow tester from 10.sup.3 to 10.sup.6 poise at a temperature within
the temperature range of from 120.degree. C. to 150.degree. C., and
an absolute value of the inclination of a graph is not more than
0.50 ln (poise)/.degree.C. when the natural logarithms ln.eta.' of
the melt viscosity at 120.degree. C. and 150.degree. C. are plotted
with respect to the temperatures.
7. A heat fixable toner according to claim 1, wherein;
said binder resin contains a linear polyester resin having an acid
value of less than 5 mg.KOH/g and a non-linear polyester resin
having an acid value of from 5 to 60 mg.KOH/g, and contains an
organic metal compound of a valence of two or more in an amount of
from 0.2 to 10 parts by weight based on 100 parts by weight of the
binder resin; and
said graft-modified polyolefin comprises a low-melting
graft-modified polyolefin having a number average molecular weight
Mn of not more than 1.0.times.10.sup.3, a weight average molecular
weight Mw of not more than 2.5.times.10.sup.3, an Mw/Mn of not more
than 3.0, and a melting point of from 60.degree. to 120.degree.
C.
8. A heat fixable toner according to claim 1, wherein a grafting
agent is used in an amount of from 1 to 50 parts by weight based on
100 parts by weight of the .alpha.-olefin monomer, to graft-modify
said .alpha.-olefin polymer.
9. A heat fixable toner according to claim 1, wherein said styrenic
monomer comprises a monomer selected from the group consisting of
styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,
.alpha.-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene,
p-n-butylstyrene, p-tert-butylstyrene, p-n-dodecylstyrene,
p-phenylstyrene and p-chlorostyrene.
10. A heat fixable toner according to claim 1, wherein said
methacrylic monomer comprises a monomer selected from the group
consisting of methyl methacrylate, ethyl methacrylate, propyl
methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl
methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate,
stearyl methacrylate, dodecyl methacrylate, phenyl methacrylate,
dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,
2-hydroxyethyl methacrylate, 2,2,2-trifluoroethyl methacrylate, and
glycidyl methacrylate.
11. A heat fixable toner according to claim 1, wherein said
methacrylic monomer comprises a monomer selected from the group
consisting of methyl acrylate, ethyl acrylate, propyl acrylate,
n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, lauryl
acrylate, stearyl acrylate, dodecyl acrylate, 2-ethylhexyl
acrylate, phenyl acrylate, 2-chloroethyl acrylate, 2-hydroxyethyl
acrylate, cyclohexyl acrylate, dimethylaminoethyl acrylate,
diethylaminoethyl acrylate, dibutylaminoethyl acrylate, 2-ethoxy
acrylate and 1,4-butanediol diacrylate.
12. A heat fixable toner according to claim 1, wherein said maleic
monomer comprises a monomer selected from the group consisting of
maleic acid, monoethyl maleate, diethyl maleate, monopropyl
maleate, dipropyl maleate, monobutyl maleate, dibutyl maleate and
di-2-ethylhexyl maleate.
13. A heat fixable toner according to claim 1, wherein said fumaric
monomer comprises a monomer selected from the group consisting of
fumaric acid, monoethyl fumarate, diethyl fumarate, dibutyl
fumarate and di-2-ethylhexyl fumarate.
14. A heat fixable toner according to claim 1, wherein said
itaconic monomer comprises a monomer selected from the group
consisting of itaconic acid, monoethyl itaconate and diethyl
itaconate.
15. A heat fixable toner according to claim 1, wherein said
citraconic monomer comprises a monomer selected from the group
consisting of citraconic acid, monoethyl citraconate and diethyl
citraconate.
16. A heat fixable toner according to claim 1, wherein said
.alpha.-olefin polymer comprises a member selected from the group
consisting of homopolymer of .alpha.-olefins, copolymer of two or
more kinds of .alpha.-olefins and an oxide thereof.
17. A heat fixable toner according to claim 16, wherein said
.alpha.-olefin comprises a member selected from the group
consisting of ethylene, propylene, 1-butene, 1-hexane, 1-decene,
and 4-methyl-1-pentene.
18. A heat fixable toner comprising a binder resin and a
graft-modified polyolefin as a release agent, wherein said binder
resin comprises a bisphenolic polyester resin, said polyester resin
being obtained by co-condensation of an acid component containing
aromatic dicarboxylic acids in amounts of at least 30 mol % based
on the total of said acid component and an alcohol component
containing etherified bisphenols in amounts of at least 80 mol %
based on the total of said alcohol component; and
said graft-modified polyolefin comprises an .alpha.-olefin polymer
graft-modified with a grafting agent of from 0.1 to 100 parts by
weight based on 100 parts by weight of the .alpha.-olefin polymer,
wherein said grafting agent comprises from 20 to 80% by weight of
an styrenic monomer and from 80 to 20% by weight of at least one
monomer selected from the group consisting of methacrylic monomer,
acrylic monomer, maleic monomer, fumaric monomer, itaconic monomer
and citraconic monomer.
19. A heat fixable toner according to claim 18, wherein said toner
has a melt viscosity .eta.' measured with an overhead flow tester
from 10.sup.3 to 10.sup.6 poise at a temperature within the
temperature range of from 120.degree. C. to 150.degree. C., and an
absolute value of the inclination of a graph is not more than 0.50
ln (poise)/.degree.C. when the natural logarithms ln.eta.' of the
melt viscosity at 120.degree. C. and 150.degree. C. are plotted
with respect to the temperatures.
20. A heat fixable toner according to claim 18, wherein said toner
has a melt viscosity of from 1 to 250 centipoise at 160.degree.
C.
21. A heat fixable toner according to claim 18, wherein said
graft-modified polyolefin is present in said toner in an amount of
from 0.1 to 20% by weight based on the weight of the binder
resin.
22. A heat fixable toner according to claim 18, wherein said
graft-modified polyolefin is present in said toner in an amount of
from 0.5 to 10% by weight based on the weight of the binder
resin.
23. A heat fixable toner according to claim 18, wherein a grafting
agent is used in an amount of from 1 to 50 parts by weight based on
100 parts by weight of the .alpha.-olefin monomer to graft-modify
said .alpha.-olefin polymer.
24. A heat fixable toner according to claim 18, wherein said
styrenic monomer comprises a monomer selected from the group
consisting of styrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, .alpha.-methylstyrene, 2,4-dimethylstyrene,
p-ethylstyrene, p-n-butylstyrene, p-tert-butylstyrene,
p-n-dodecylstyrene, p-phenylstyrene and p-chlorostyrene.
25. A heat fixable toner according to claim 18, wherein said
methacrylic monomer comprises a monomer selected from the group
consisting of methyl methacrylate, ethyl methacrylate, propyl
methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl
methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate,
stearyl methacrylate, dodecyl methacrylate, phenyl methacrylate,
dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,
2-hydroxyethyl methacrylate, 2,2,2-trifluoroethyl methacrylate, and
glycidyl methacrylate.
26. A heat fixable toner according to claim 18, wherein said
methacrylic monomer comprises a monomer selected from the group
consisting of methyl acrylate, ethyl acrylate, propyl acrylate,
n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, lauryl
acrylate, stearyl acrylate, dodecyl acrylate, 2-ethylhexyl
acrylate, phenyl acrylate, 2-chloroethyl acrylate, 2-hydroxyethyl
acrylate, cyclohexyl acrylate, dimethylaminoethyl acrylate,
diethylaminoethyl acrylate, dibutylaminoethyl acrylate, 2-ethoxy
acrylate and 1,4-butanediol diacrylate.
27. A heat fixable toner according to claim 18, wherein said maleic
monomer comprises a monomer selected from the group consisting of
maleic acid, monoethyl maleate, diethyl maleate, monopropyl
maleate, dipropyl maleate, monobutyl maleate, dibutyl maleate and
di-2-ethylhexyl maleate.
28. A heat fixable toner according to claim 18, wherein said
fumaric monomer comprises a monomer selected from the group
consisting of fumaric acid, monoethyl fumarate, diethyl fumarate,
dibutyl fumarate and di-2-ethylhexyl fumarate.
29. A heat fixable toner according to claim 18, wherein said
itaconic monomer comprises a monomer selected from the group
consisting of itaconic acid, monoethyl itaconate and diethyl
itaconate.
30. A heat fixable toner according to claim 18, wherein said
citraconic monomer comprises a monomer selected from the group
consisting of citraconic acid, monoethyl citraconate and diethyl
citraconate.
31. A heat fixable toner according to claim 18, wherein said
.alpha.-olefin polymer comprises a member selected from the group
consisting of homopolymer of .alpha.-olefins, copolymer of two or
more kinds of .alpha.-olefins and an oxide thereof.
32. A heat fixable toner according to claim 31, wherein said
.alpha.-olefin comprises a member selected from the group
consisting of ethylene, propylene, 1-butene, 1-hexane, 1-decene,
and 4-methyl-1-pentene.
33. A heat fixable toner according to claim 18, including a
coloring agent and wherein:
said bisphenolic polyester resin comprises a polyester resin having
an acid value of from 5 to 60, formed of:
(A) an etherified bisphenol;
(B) not less than 30 mol % of an aromatic dicarboxylic acid, in all
acid components;
(C) 5 to 40% by weight of an alkenyl-substituted dicarboxylic acid,
an alkyl-substituted dicarboxylic acid or mixtures thereof, based
on the total amount of acids; and
(D) a polycarboxylic acid with three or more carboxylic groups, a
polyol with three or more hydroxy groups, or mixtures thereof;
an organic metal compound comprising a metal of valence of two or
more is present in an amount of from 0.2 to 6% by weight based on
the weight of the binder resin;
said graft-modified polyolefin has a melt viscosity of from 1 to
250 centipoise at 160.degree. C. and is present in an amount of
from 0.1 to 20% by weight based on the weight of the binder resin;
and
said toner has a melt viscosity .eta.' measured with an overhead
flow tester from 10.sup.3 to 10.sup.6 poise at a temperature within
the temperature range of from 120.degree. C. to 150.degree. C., and
an absolute value of the inclination of a graph is not more than
0.50 ln (poise)/.degree.C. when the natural logarithms ln.eta.' of
the melt viscosity at 120.degree. C. and 150.degree. C. are plotted
with respect to the temperatures.
Description
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a heat fixable toner used for
obtaining a fixed toner image by forming a toner image using an
image forming process such as electrophotography, electrostatic
printing or magnetic recording, and heat-fixing the formed toner
image on a recording medium. It also relates to a heat fixing
method making use of such a toner.
2. Related Background Art
As a method of fixing a visible image of toner onto a recording
medium, a heat-roll fixing system is widely used, in which a
recording medium retaining thereon a toner visible image which has
not been fixed is heated while it is held and carried between a
heat roller maintained at a given temperature and a pressure roller
having an elastic layer and coming into pressure contact with the
heat roller.
A belt fixing system is known, as disclosed in U.S. Pat. No.
3,578,797.
The above conventional heat-roll fixing that has been hitherto
widely used, however, has the following disadvantages:
(1) A time during which an image-forming operation is prohibited,
i.e., what is called a waiting time, is required until the heat
roller reaches the given temperature.
(2) The heat roller must be maintained at an optimum temperature in
order to prevent poor fixing caused by the variations of the
heat-roller temperature that may occur when the recording medium is
passed or because of other external factors, and also to prevent
the transfer of toner to the heat roller, i.e., what is called the
offset phenomenon. This makes it necessary to make large the heat
capacity of the heat roller or a heater element, which requires a
large electric power.
(3) After the recording medium has been passed over the heat
roller, the recording medium and the toner on the recording medium
are slowly cooled because of a high temperature of the heat roller.
This results in a high adhesion of the toner. Thus, conjointly with
the curvature of the roller also, there may often occur offset, or
paper jam caused by the rolling-up of the recording medium to the
roller.
(4) A protective member must be provided on account of safety since
there is a possibility of directly touching the high-temperature
heat roller.
The above problems (1) and (2) in the heat-roll fixing are not
fundamentally solved also in the belt fixing system disclosed in
U.S. Pat. No. 3,578,797.
Japanese Patent Application Laid-open No. 63-313182, previously
proposed by the present applicant, provides an image forming
apparatus with a shorter waiting time and a low power consumption,
comprising a fixing unit in which a toner visible image is heated
through a movable heat-resistant sheet by means of a heating
element having a low heat capacity, pulsewise generating heat by
electrification, and is thus fixed to a recording medium. Japanese
Patent Application Laid-open No. 1-187582, previously proposed by
the present applicant, provides a fixing unit for heat-fixing a
toner visible image to a recording medium through a heat-resistant
sheet, wherein said heat-resistant sheet comprises a heat-resistant
layer and a release layer or a low-resistant layer, thereby
effectively preventing the offset phenomenon.
In addition to the factors in the above fixing apparatus, however,
achievement of both the fixing performance of an excellent toner
visible image to a recording medium and the prevention of offset
and simultaneous realization of a fixing method with a shorter
waiting time and a low power consumption greatly depend on the
properties of a toner.
As materials suited for a low-temperature fixable toner, polyester
resins with a low molecular weight have attracted notice. An
attempt to use a polyester resin as a binder for a toner is seen in
U.S. Pat. Nos. 3,590,000 and 3,681,106, and Japanese Pat.
Publications No. 46-12680 and No. 52-25420. Since, however, melt
viscosity of the resin is lowered when the molecular weight is made
smaller with the aim of lower-temperature fixing, the temperature
control of a fixing device is so adjusted as to yield a temperature
at which a toner can be sufficiently fixed. This may cause the
offset phenomenon in which the toner is melt-adhered not only to
paper, but also onto a heater element.
Concerning the prevention of offset in respect of a toner
comprising a polyester resin as a main binder, Japanese Patent
Publication No. 52-25420 proposes a method in which a polymer is
made non-linear by mixture of a polyol having three or more
hydroxyl groups or a poly acid to improve its viscoelasticity so
that the offset resistance at the time of fixing can be improved.
However, making the polymer non-linear until the toner can have a
sufficient offset resistance may result in a rise of its fixing
point, and hence this method is not suitable for a toner intended
to be fixed at a low temperature.
As proposed in Japanese Patent Application Laid-open No. 59-9669,
it has been attempted to mix a polyvalent metal compound so as to
give a cross-linked structure by virtue of metal ions, so that the
polymer chains can mutually act to change melt viscoelasticity,
thus preventing the offset. The polyvalent metal compound, however,
has so low a specific resistance compared to resins that the static
chargeability of a toner may be lowered. For this reason, if the
prevention of offset relies only on the cross-linking of the
polyvalent metal compound, the compound is necessarily added in a
larger amount, which tends to lower the development performance of
the toner. In this way, the low-temperature fixability and the
offset resistance are performances that conflict with each other,
and it is very difficult to combine these. As a means for solving
this problem, Japanese Patent Applications Laid-open No. 60-67958
and No. 64-15755 propose a method in which a low-molecular weight
polyester for achieving the low-temperature fixing and a
high-molecular weight polyester for achieving the offset resistance
are blended. This has made it possible to achieve the
low-temperature fixing while keeping the offset resistance when
compared with conventional polyesters.
However, in an attempt to achieve a better low-temperature fixing,
the low-molecular weight polyester to be blended must be made to
have a low melting point, resulting in a lowering of the offset
resistance. When a polyester made to have a molecular weight high
enough to well compensate for this lowering is mixed with the
low-molecular weight polyester, it is difficult for the components
added to a toner as exemplified by a coloring agent, to be
uniformly dispersed and it has been impossible to obtain good
development performance.
Japanese Patent Application Laid-open No. 60-4947 proposes a toner
in which an organic metal compound is added to a mixture of a
linear polyester and a non-linear polyester resin, which is then
cross-linked. In this instance, however, both of the linear
polyester and the non-linear polyester undergo cross-linking, and
the non-linear polyester, in particular, is made high-molecular.
Hence, there is room for further improvement when low-temperature
fixing is desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a heat fixable
toner that has solved the above problems.
Another object of the present invention is to provide a toner that
can be well fixed at a low temperature, can save energy, can
prevent offset and also can promise a broad region of
fixability.
Still another object of the present invention is to provide a toner
that causes no blocking when it is stored and also when it is
used.
A further object of the present invention is to provide a toner
that causes no melt-adhesion onto a toner carrying member or a
photosensitive member when used in various states in any
environment.
A still further object of the present invention is to provide a
toner having superior development performance, capable of obtaining
an image quality that has a sufficiently high image density, is
rich in sharpness and resolution and is free from ground fog.
A still further object of the present invention is to provide a
toner that can be readily produced, has a good production
efficiency, can be stably produced and enjoys a low cost.
A still further object of the present invention is to provide a
toner used for a novel heat-fixing method that requires
substantially no, or only a very short, waiting time and also a low
power consumption, can prevent the offset phenomenon from occurring
and also can achieve good fixing of a toner image to a recording
medium, and a fixing method making use of such a toner.
A still further object of the present invention is to provide a
heat fixing method that employs no high-temperature revolving
roller, thus requiring no heat-resistant special bearing.
A still further object of the present invention is to provide a
heat fixing method using a fixing device so constituted as to
prevent direct touch to high-temperature parts, thus achieving
higher safety or requiring no protective members.
To achieve the above objects, the present invention provides a heat
fixable toner comprising a binder resin and a release agent,
wherein said binder resin comprises a polyester resin and said
release agent comprises a graft-modified polyolefin.
The present invention also provides a heat fixing method comprising
heat-fixing a toner image formed on a recording medium, to said
recording medium by means of a heater element stationarily
supported and a pressure member that is opposed to and in pressure
contact with said heater element and brings said recording medium
into close contact with said heater element through a film
interposed between them, wherein said toner comprises a binder
resin and a release agent; said binder resin comprising a polyester
resin and said release agent comprising a graft-modified
polyolefin.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic cross section of an overhead-type flow tester
used for measuring the melt viscosity of toner or binder resin.
FIG. 2 is a graphic representation concerning the inclination of
the natural logarithms ln.eta. of the viscosity of toner or binder
resin, with respect to temperature.
FIG. 3 is a graphic representation of an endothermic peak
temperature T.sub.D of a toner, measured by differential thermal
analysis (using DSC).
FIG. 4A is a schematic cross section of a fixing device used for
carrying out the fixing method of the present invention, and FIG.
4B is a schematic cross section of a fixing device used for
carrying out the fixing method according to another embodiment of
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The toner of the present invention contains at least a polyester
resin as a binder resin and a graft-modified polyolefin as a
release agent.
Preferred examples of the polyester resin used in the present
invention will be described below.
The polyester resin includes, for example, a polyester resin
obtained by co-condensation polymerization of an etherified
bisphenol with a carboxylic acid or its derivative, including a
carboxylic acid with two or more carboxylic groups, an anhydride
thereof or a lower alkyl ester thereof. This polyester resin may
preferably have the properties that the melt viscosity .eta.'
measured with an overhead-type flow tester is from 10.sup.3 to
10.sup.6 poise at a temperature within the temperature range of
from 80.degree. C. to 120.degree. C., and an absolute value of the
inclination of a graph is not more than 0.50 ln (poise)/.degree.C.
when the natural logarithms ln.eta.' of the melt viscosity at
80.degree. C. and 120.degree. C. are plotted with respect to the
temperatures.
In the present invention, the viscosity can be measured using an
overhead-type flow tester as illustrated in FIG. 1 (Shimadzu Flow
Tester CFT-500 Type). In the first place, about 1.5 g of a sample 3
molded using a pressure molder is extruded from a nozzle 4 of 1 mm
in diameter and 1 mm in length under application of a load of 10
kgf at a given temperature using a plunger 1, and thus the quantity
of the fall of the plunger (the rate of flow-out) of the flow
tester is measured. This rate of flow-out is measured at each
temperature (at intervals of 5.degree. C. within the temperature
range of from 80.degree. C. to 150.degree. C.). The apparent
viscosity .eta.' can be calculated from the resulting values, based
on the following equation. ##EQU1## .eta.': Apparent viscosity
(poise) TW': Apparent slide reaction on tube wall
(dyne/cm.sup.2)
DW': Apparent slide speed on tube wall (1/sec)
Q: Rate of flow-out (cm.sup.3 /sec=ml/sec)
P: Extrusion pressure (dyne/cm.sup.2) [10 kgf=980.times.10.sup.4
dyne]
R: Radius of nozzle (cm)
L: Length of nozzle (cm)
A melt viscosity more than 10.sup.6 poise at 80.degree. C. to
150.degree. C., of the binder resin polyester used for the toner
may result in an increase in power consumption even in the
heat-fixing method of the present invention, bringing about
difficulty in quick start.
On the other hand, a melt viscosity less than 10.sup.3 poise at
80.degree. C. to 150.degree. C. may make conspicuous the problems
of bleed-through in transfer paper caused by the excessive fusion
of toner and bleeding of image due to strike-through or spread of
the fused toner.
The absolute value of the inclination of the natural logarithms
ln.eta.' of the melt viscosity .eta.' in the temperature range of
from 80.degree. C. to 150.degree. C., with respect to the
temperatures, reflects the sensitiveness of the viscosity of the
polyester resin of the present invention to the temperature
variations. A value more than 0.50 ln (poise)/.degree.C. tends to
cause the offset to the recording medium such as a film
An alcohol component which is a component material of the polyester
resin according to the present invention may preferably include
etherified bisphenols, which contribute the retention of impact
resistance and abrasion resistance required as a toner and may not
adversely affect the electrophotographic performances other than
the fixing performance.
In the present invention, the "inclination" of the viscosity is a
value obtained when, as FIG. 2 shows, a measuring point at t.sub.a
.degree.C. and a measuring point at tb.degree.C. in the graph are
connected by a straight line and the "inclination" is calculated
from the equation: ##EQU2## This is used in approximation as the
"inclination" of a slope, wherein the ln.eta.a' represents a value
corresponding to the natural logarithm of the viscosity at t.sub.a
.degree.C., and ln.eta.b' represents a value at t.sub.b
.degree.C.
Those which can be used as the etherified diphenols, i.e., the
materials of the polyester resin serving as the binder resin used
in the toner of the present invention, are exemplified by
polyoxystyrene (6)-2,2-bis(4-hydroxyphenyl)propane,
polyhydroxybutylene (2)-2,2-bis(4-hydroxyphenyl) propane,
polyoxyethylene (3)-2,2-bis(4-hydroxyphenyl)propane,
polyoxypropylene (3)-bis(4-hydroxyphenyl)thioether, polyoxyethylene
(2)-2,6-dichloro-4-hydroxyphenyl,
2',3',6'-trichloro-4'-hydroxyphenylmethane, polyoxypropylene
(3)-2-bromo-4-hydroxyphenyl, 4-hydroxyphenyl ether, polyoxyethylene
(2,5)-p,p-bisphenol, polyoxybutylene
(4)-bis(4-hydroxyphenyl)ketone, polyoxystyrene
(7)-bis(4-hydroxyphenyl)ether, polyoxypentylene
(3)-2,2-bis(2,6-diodo-4-hydroxyphenyl)propane, and polyoxypropylene
(2,2)-2,2-bis(4-hydroxyphenyl)propane.
A group of the etherified diphenols includes etherified bisphenols.
A preferred group of the etherified bisphenols includes those
formed into ethoxy or propoxy, which may have 2 or 3 mols of
oxyethylene or oxypropylene per mol of bisphenol and may have a
propylene or sulfone group as a substituent. Examples of this group
are polyoxyethylene (2,5)-bis(2,6-dibromo-4-hydroxyphenyl)sulfone,
polyoxypropylene (3)-2,2bis(2,6-difluoro-4-hydroxyphenyl)propane,
and polyoxyethylene (1,5)-polyoxypropylene
(1,0)-bis(4-hydroxyphenyl)sulfone.
Other preferred examples of the etherified bisphenols are
polyoxypropylene-2,2'-bis(4-hydroxyphenyl)propane, and
polyoxyethylene- or
polyoxypropylene-2,2-bis(4-hydroxy-2,6-dichlorophenyl)propane (the
number of the oxyalkylene unit is 2.1 to 2.5 per mol of
bisphenol).
The carboxylic acids with two or more carboxylic groups, which are
component materials of the polyester resin according to the present
invention, include aromatic carboxylic acids and other carboxylic
acids, either of which can be used. Not less than 95 mol % of the
acid component may preferably be held by dicarboxylic acids. It is
possible to use aromatic dicarboxylic acids as exemplified by
terephthalic acid, isophthalic acid, phthalic acid,
diphenyl-p,p'-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,
naphthalene-2,6-dicarboxylic acid,
diphenylmethane-p,p'-dicarboxylic acid,
benzophenone-4,4'-dicarboxylic acid, and
1,2-diphenoxyethane-p,p'-dicarboxylic acid. Acids other than these
include maleic acid, fumaric acid, glutaric acid,
cyclohexanecarboxylic acid, succinic acid, malonic acid, adipic
acid, mesaconic acid, citraconic acid, sebacic acid, anhydrides of
these acids, and lower-alkyl esterified compounds of these
acids.
The polycarboxylic acids with three or more carboxylic groups can
also be used. They are exemplified by trimellitic acid,
pyromellitic acid, cyclohexanetricarboxylic acid,
2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic
acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic
acid, 1,3-dicarboxyl-2-methylenecarboxylpropane,
1,3-dicarboxyl-2-methyl-2-methylenecarboxylpropane,
tetra(methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic
acid, and anhydrides of these. Lower-alkyl esterified compounds of
these may also be used in a small amount. Polyols having three or
more hydroxyl groups may also be used if it is in a small amount.
They include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan,
pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose,
1,2,4-mesitatriol, glycerol, 2-methylpropanetriol,
2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane,
1,3,5-trihydroxymethylbenzene, erythro-1,2,3-butanetriol, and
threo-1,2,3-butanetriol.
Other preferred polyester resins include polyester resins with an
acid value of from 5 to 60, comprised of;
(A) an etherified bisphenol;
(B) not less than 30 mol % of an aromatic dicarboxylic acid, in all
acid components;
(C) 5 to 40% by weight of an alkenyl-substituted dicarboxylic acid
and/or an alkyl-substituted dicarboxylic acid, based on the total
amount of acids; and
(D) a polycarboxylic acid with three or more carboxylic groups
and/or a polyol with three or more hydroxyl groups.
In the present invention, the toner can be preferably heat-fixed to
the recording medium at a lower power consumption when a toner is
used which contains at least i) a polyester resin with an acid
value of from 5 to 60, comprising the etherified diphenols and the
aromatic dicarboxylic acids as basic skeletons, where the polymer
skeletons are made to have network structures by the polycarboxylic
acids with three or more carboxylic groups and/or polyols with
three or more hydroxyl groups, and the alkenyl-substituted
dicarboxylic acids and/or alkyl-substituted dicarboxylic acids are
introduced as soft segments and ii) an organic metal compound
containing a metal having a valence of two or more, used in an
amount of from 0.2 to 6% by weight based on the resin.
An amount of the above soft segments which is less than 5% by
weight based on the total amount of acids tends to result in an
increase in the power consumption required for the heat fixing. On
the other hand, an amount exceeding 40% by weight tends to make
stronger the agglomeration force between toner particles to lower
storage stability. The polycarboxylic acids, the component by which
the polymer skeletons are made to have network structures, may
preferably be contained in the polyester in an amount of from 5 to
30% by weight. The polyols may preferably be contained in an amount
of not more than 5% by weight.
The total amount of the polycarboxylic acids and polyols may
preferably be not more than 40% by weight. An amount more than 40%
by weight may result in a lowering of the moisture resistance of
the toner and make charge characteristics unstable because of
environmental variations, bringing about defects at the time of the
image formation (at the time of development or transfer) before the
fixing. It may further result in an increase in the cost for the
pulverization in the step of preparing the toner, and also
requires, as a matter of course, a larger energy for achieving the
heat fixing of the toner.
On the other hand, the total amount of the polycarboxylic acids may
preferably be not less than 10% by weight in the polyester. An
amount less than that may make the tendency of excessive fusion of
toner begin to appear in the step of heat fixing. An amount less
than 5% by weight tends to cause the penetration into the recording
medium such as transferring paper, the bleed-through, or the
bleeding of image because of the spread of fused toner.
Taking account of electrophotographic performances such as charge
characteristics, durability and transfer performance which are
required for the toner, among the main components of the polyester,
it is preferred for the aromatic dicarboxylic acids as the acid
component to comprise not less than 30 mol % and more preferably
not less than 40 mol % in all the acid components, and for the
etherified diphenols as the alcohol component to comprise not less
than 80 mol % and more preferably not less than 90 mol % in all the
alcohol components.
The above polyester resins may be used as a binder resin, and an
organic metal compound containing a metal of a valence of two or
more may be added in a small amount in the step of heat-kneading at
the time the toner is prepared, so that in the heat fixing method
of the present invention the excessive fusion of toner, in
particular, can be effectively prevented and the problems such as
the penetration into the recording medium, the bleed-through and
the bleeding of image because of the spread of fused toner can be
more effectively prevented from occurring.
According to the studies made by the present inventors, a "weak
cross-linked structure", different from the one attributable to the
network-structure forming component in the component materials of
the polyester resin, can be brought in the toner by a metal ion, so
that there can be a very little increase in the consumption of the
power required for the fixing. However, the above effect obtained
by the present invention, attributable to the organic metal
compound containing a metal of a valence of two or more, can be
attained when the polyester resin contains the aromatic components
in a large amount. When the polyester resin has an acid value of
from 5 to 60, the metal compound can be added in a smaller amount,
thus resulting in no concurrence of the problems such as an
increase in power consumption and a lowering of moisture resistance
of the toner.
Accordingly, the metal compound in the present invention may be
added in an amount of from 0.2 to 6% by weight, and more preferably
from 1 to 5% by weight, based on the polyester resin. An amount
less than 0.2% by weight may bring about no substantial effect, and
an amount more than 6% by weight may cause an increase in the power
consumption at the time of the fixing because of an increase in the
heat capacity of the toner itself, like the case when an inorganic
filler is added in a large amount. This may considerably lessen the
static chargeability of the toner because of the incorporation of
the metal compound having a lower specific resistance than that of
the polymer, tending to result in a lowering of development
performance. A lowering of moisture resistance similarly tends to
occur.
In the present invention, it is preferred that the above specific
polyester resin is used as a main binder resin and the toner
containing the metal compound have the properties that the melt
viscosity .eta.' measured with an overhead-type flow tester is from
10.sup.3 to 10.sup.6 poise at a temperature within the temperature
range of from 120.degree. C. to 150.degree. C. and an absolute
value of the inclination of a graph is not more than 0.50 ln
(poise)/.degree.C. when the natural logarithms ln.eta.' of the melt
viscosity at 120.degree. C. and 150.degree. C. are plotted with
respect to the temperatures. This enables fixing of toner to a
recording medium at a low power consumption without causing its
offset to a film.
If the total amount of of the network-structure forming components
in the polyester of the present invention is 35% by weight or more,
or the organic metal compound containing a metal of a valence of
two or more, contained in the toner, is added in an amount of 10%
by weight or more based on the resin, the melt viscosity of the
toner may often exceed 10.sup.5 poise even at 150.degree. C.
On the other hand, a melt viscosity less than 10.sup.3 poise at
120.degree. C. to 150.degree. C. may make conspicuous the
disadvantages (such as bleed-through, and bleeding of image) caused
by the excessive fusion of toner.
If the total amount of the network-structure forming components in
the polyester of the present invention becomes less than 5% by
weight, or the organic metal compound containing a metal of a
valence of two or more, contained in the toner, is added in an
amount of 0.2% by weight or more based on the resin, the melt
viscosity may sometimes become less than 10.sup.3 poise even at
120.degree. C.
The absolute value of the inclination of the natural logarithms
ln.eta.' of the melt viscosity .eta.' at 120.degree. C. and
150.degree. C. of the toner of the present invention, with respect
to the temperatures, reflects the sensitiveness of the viscosity of
the polyester resin of the present invention to the temperature
variations. An absolute value more than 0.50 ln (poise)/.degree.C.
of this inclination tends to cause the offset to the film, moreover
bringing about an excessive gloss of fixed images to lower the
image quality level.
This inclination also depends on the amount of the
network-structure forming components and amount of the soft
segments in the polyester resin of the present invention, and also
the amount of the organic metal compound containing a metal of a
valence of two or more, added in the toner of the present
invention. It also depends on the proportion of these. Use of these
in the amounts within the range of what is claimed in the present
invention can achieve the fixing performance, offset resistance,
and image forming performance in a good state in the heat-fixing
method of the present invention.
The etherified diphenol and the aromatic dicarboxylic acid include
those as previously described.
The alkenyl-substituted dicarboxylic acid or alkyl-substituted
dicarboxylic acid includes maleic acid, fumaric acid, adipic acid,
succinic acid, glutaric acid, sebacic acid or azelaic acid
substituted with an alkenyl group or alkyl group having 6 to 18
carbon atoms, and anhydrides or esters thereof. Particularly
preferred are n-dodecenyl succinate, isododecenyl succinate,
n-dodecyl succinate, isododecyl succinate, isooctyl succinate,
n-octyl succinate, and n-butyl succinate.
The polycarboxylic acid with three or more carboxylic groups and
polyols with three or more hydroxyl groups include those as
previously described.
The organic metal compound used in combination with the polyester
resin includes organic salts or complexes containing the metal of a
valence of two or more. Effective metal species include polyvalent
metals such as Al , Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb,
Sn, Sr and Zn. The organic metal compound effectively includes
carboxylates, alkoxylates, organic metal complexes or chelate
compounds of the above metals. Examples thereof may preferably
include zinc acetate, magnesium acetate, calcium acetate, aluminum
acetate, magnesium stearate, calcium stearate, aluminum stearate,
aluminum isopropoxide, aluminum acetylacetate, iron(II)
acetylacetonate, and chromium 3,5-ditertiarybutyl stearate. In
particular, acetylacetone metal complexes, or salicylic acid metal
salts are preferred.
Other preferred polyester resin composition also includes a mixture
containing a linear polyester resin having an acid value of less
than 5 mg.KOH/g and a non-linear polyester resin having an acid
value of from 5 to 60 mg.KOH/g, and also containing an organic
metal compound of a valence of two or more in an amount of from 0.2
to 10 parts by weight based on 100 parts by weight of the polyester
resin or the binder resin.
In the present invention, at the time when the linear polyester
resin and the non-linear polyester resin are mixed, or after they
have been mixed, an additive in toner particles, such as a coloring
agent, and the organic metal compound comprising a metal of a
valence of two or more are mixed, and metal cross-linking is
carried out.
In order to achieve the low-temperature fixing, the acid value of
the linear polyester resin must be less than 5 mg.KOH/g. An acid
value not less than 5 mg.KOH/g may cause metal cross-linking,
resulting in a high molecular weight of the linear polyester resin.
This makes it difficult to effectively lower the fixing point. In
order to retain the offset resistance, the acid value of the
non-linear polyester resin must be 5 to 60 mg.KOH/g. An acid value
less than 5 mg.KOH/g makes the metal cross-linking insufficient,
and makes it impossible to obtain a satisfactory offset resistance.
An acid value more than 60 mg.KOH/g may result in an excessive
progress of non-linearization, often making it difficult to carry
out the low-temperature fixing or often making moisture resistance
poor because of an unreacted acid.
The non-linear polyester resin after mixing is further
non-linearized by the metal cross-linking, and hence it is
unnecessary for the non-linear polyester resin before mixing to be
cross-linked to have a sufficient offset resistance. Thus, in the
mixture comprising the non-linear polyester resin not cross-linked
to have a sufficient offset resistance and the linear polyester
resin, it is possible for the additive such as a coloring agent to
be uniformely mixed and dispersed.
The linear polyester resin and the non-linear polyester resin may
preferably be mixed to form a solution or mixed at the time of
kneading. The acid value can be measured according to JIS
K-0070.
In a more preferred embodiment, a toner comprised of at least one
low-melting graft-modified polyolefin release agent having a number
average molecular weight (Mn) of not more than 1.0.times.10.sup.3,
and preferably from 400 to 700, a weight average molecular weight
(Mw) of not more than 2.5.times.10.sup.3, and preferably from 700
to 1,500, an Mw/Mn of not more than 3.0, and preferably not more
than 2.0, and a melting point of from 60.degree. to 120.degree. C.,
and preferably from 60.degree. to 100.degree. C., is used in the
above binder resin. This makes it possible to carry out the heat
fixing of a toner to a recording medium at a lower power
consumption and lower temperature without causing offset.
Intensive studies made by the present inventors have revealed that
what is required is a release agent which renders release
properties at a lower temperature with respect to the
low-temperature melting, linear polyester resin which enables the
low-temperature fixing, that the temperature at which the release
agent renders release properties correlates with the melting point
of the release agent, and that a release agent having a lower
melting point is more advantageous for the low-temperature fixing.
When, however, a release agent with a low melting point is used,
the release agent makes poor the blocking resistance of a toner and
has an undesired influence of carrier filming when the product is
used as a two-component type developer. Now, at least one release
agent is made to have a number average molecular weight (Mn) of not
more than 1.0.times.10.sup.3, a weight average molecular weight
(Mw) of not more than 2.5.times.10.sup.3 and an Mw/Mn of not more
than 3.0, which are relatively sharp. As a result, it has been made
clear that the blocking resistance can thereby be improved, the
release agent renders release properties at a lower temperature,
and the good performance without causing the offset phenomenon can
be obtained.
The low-temperature fixing can be achieved to a certain extent when
the low-melting temperature release agent as described above is
used in combination. It, however, has been found that the above
problems can be eliminated and a good development performance and
further low-temperature fixing performance can be achieved when the
low-melting polyolefin release agent is graft-modified in order to
further improve the dispersion of the release agent in the mixed
resin of the linear polyester resin and non-linear polyester
resin.
In the present invention, the molecular weight distribution of the
low-melting graft modified polyolefin release agent can be measured
by GPC (gel permeation chromatography) under the following
conditions. Condition for measurement by GPC:
Apparatus: LC-GPC, 150 C (Waters Co.)
Column: GMH6 (Toyo Soda Manufacturing Co., Ltd.), 60 cm
Column temperature: 140.degree. C.
Solvent: o-dichlorobenzene
Under the above measuring conditions, the molecular weight
distribution possessed by a sample is calculated from the relation
between a logarithmic value of a calibration curve prepared using a
polyethylene standard sample and the number of count.
In the present invention, the melting point of the above release
agent is measured using a differential scanning calorimeter DSC-7
(manufactured by Perkin-Elmer Co.) to determine an endothermic peak
in the DSC, which peak is regarded as a maximum melting peak
value.
The linear polyester resin used in the present invention can be
produced by condensation polymerization of a bifunctional
carboxylic acid with a diol according to a conventional method.
The bifunctional carboxylic acid refers to a dibasic carboxylic
acid, an anhydride and an ester of the dibasic carboxylic acid, and
a derivative thereof, including, for example, terephthalic acid,
isophthalic acid, phthalic acid, diphenyl-p,p'-dicarboxylic acid,
naphthalene-2,7-dicarboxylic acid, naphthalene-2,6-dicarboxylic
acid, diphenylmethane-p,p'-dicarboxylic acid,
benzophenone-4,4'-dicarboxylic acid,
1,2-diphenoxyethane-p,p'-dicarboxylic acid, maleic acid, fumaric
acid, glutalic acid, cyclohexanecarboxylic acid, succinic acid,
malonic acid and adipic acid, or anhydrides or esterified compounds
of these.
The diol component includes alkylene glycols such as ethylene
glycol, diethylene glycol, triethylene glycol, 1,2-propylene
glycol, 1,3-propylene glycol, 1,4-butanediol,
cyclohexanedimethanol, neopentyl glycol and 1,4-butenediol,
bisphenol A, hydrogenated bisphenol A, polyoxypropylene
(2,0)-2,2-bis(4-hydroxyphenyl) propane, polyoxyethylene
(2,0)-2,2-bis(4-hydroxyphenyl)propane, 2,2'-(1,4-phenylenebisoxy)
bisethanol, 1,1'-dimethyl-2,2'-(1,4-phenylenebisoxy) bisethanol,
and 1,1,1',1'-tetramethyl-2,2'-(1,4-phenylenebisoxy)bisethanol.
The non-linear polyester resin used in the present invention can be
produced by condensation polymerization between at least one of a
polycarboxylic acid with three or more carboxylic groups and a
polyol with three or more hydroxyl groups, a bifunctional
carboxylic acid and a diol according to a conventional method.
As the polycarboxylic acid with three or more carboxylic groups and
polyol with three or more hydroxyl groups, those previously
described can be used. The bifunctional carboxylic acids and diols
used in the non-linear polyester resin may be the same as used in
the linear polyester resin described above.
As the organic metal compound used in combination with the
polyester resin composition, those previously described can be
used.
One of the features in the constitution of the heat fixable toner
of the present invention is that the toner contains a releasable
component (or the release agent). The above graft-modified
polyolefin which is the releasable component includes unsaturated
fatty acids, styrene derivatives, and polyolefin waxes
graft-modified with unsaturated fatty acid esters.
The releasable component may preferably be a polyolefin
graft-modified with an aromatic vinyl monomer with an unsaturated
fatty acid or unsaturated fatty acid ester. The releasable
component may more preferably have a melt viscosity of 1 to 250 cps
(centipoise) at 160.degree. C. and be contained in an amount of
from 0.1 to 20% by weight based on the total weight of the binder
resin.
The above polyolefin includes homopolymers of .alpha.-olefins such
as ethylene, propylene, 1-butane, 1-hexene, 1-decene, and
4-methyl-1-pentene. It also includes copolymers of two or more
kinds of .alpha.-olefins. It further includes oxides of
polyolefins.
The unsaturated fatty acid or/and unsaturated fatty acid ester used
for synthesizing the graft-modified polyolefin includes methacrylic
acid and methacrylates such as methyl methacrylate, ethyl
methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl
methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate,
lauryl methacrylate, stearyl methacrylate, dodecyl methacrylate,
phenyl methacrylate, dimethylaminoethyl methacrylate,
diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate,
2,2,2-trifluoroethyl methacrylate, and glycidyl methacrylate;
acrylic acid and acrylates such as methyl acrylate, ethyl acrylate,
propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl
acrylate, lauryl acrylate, stearyl acrylate, dodecyl acrylate,
2-ethylhexyl acrylate, phenyl acrylate, 2-chloroethyl acrylate,
2-hydroxyethyl acrylate, cyclohexyl acrylate, dimethylaminoethyl
acrylate, diethylaminoethyl acrylate, dibutylaminoethyl acrylate,
2-ethoxy acrylate, and 1,4-butanediol diacrylate; maleic acid,
fumaric acid, itaconic acid, citraconic acid, and unsaturated
dibasic acid esters such as monoethyl maleate, diethyl maleate,
monopropyl maleate, dipropyl maleate, monobutyl maleate, dibutyl
maleate, di-2-ethylhexyl maleate, monoethyl fumarate, diethyl
fumarate, dibutyl fumarate, di-2-ethylhexyl fumarate, monoethyl
itaconate, diethyl itaconate, monoethyl citraconate, and diethyl
citraconate. These can be used alone or in combination of two or
more kinds.
The aromatic vinyl monomer includes styrene, o-methylstyrene,
m-methylstyrene, p-methylstyrene, .alpha.-methylstyrene,
2,4-dimethylstyrene, p-ethylstyrene, p-n-butylstyrene,
p-tert-butylstyrene, p-n-dodecylstyrene, p-phenylstyrene, and
p-chlorostyrene. These can be used alone or in combination of two
or more kinds.
The polyolefin can be graft-modified using conventionally known
methods. For example, the polyolefin, the aromatic vinyl monomer
and the unsaturated fatty acid or unsaturated fatty acid ester
which are in the state of a solution or in a molten state may be
reacted by heating in the atmosphere, optionally under application
of pressure, and in the presence of a radical initiator. A
graft-modified polyolefin can be thus obtained. The grafting using
the aromatic vinyl monomer and the unsaturated fatty acid or
unsaturated fatty acid ester may be carried out using both at the
same time or may be carried out using them separately.
The initiator used in the grafting reaction includes, for example,
benzoyl peroxide, dichlorobenzoyl peroxide, di-tert-butyl peroxide,
lauroyl peroxide, tert-butyl perphenyl acetate, cumine pivarate,
azobisisobutylonitrile, dimethylazoisobutyrate, and dicumyl
peroxide.
As to the proportion of the grafting agent to the polyolefin, the
former may preferably be in an amount of from 0.1 to 100 parts by
weight, and more preferably from 1 to 50 parts by weight, based on
100 parts by weight of the latter. An amount less than 0.1 part by
weight can bring about little effect of grafting, and an amount
more than 100 parts by weight tends to result in loss of
advantageous properties inherent in the polyolefin.
The aromatic vinyl monomer and the unsaturated fatty acid or
unsaturated fatty acid ester may be used in a weight ratio of from
95:5 to 5:95, and more preferably from 80:20 to 20:80. An excessive
amount for the unsaturated fatty acid or unsaturated fatty acid
ester tends to result in a decrease in the releasing effect
inherent in the polyolefin. An excessive amount for the aromatic
vinyl monomer can not so much bring about an improvement in the
dispersibility of the polyolefin in the toner.
The graft-modified polyolefin used in the present invention may
preferably be added in an amount of from 0.1 to 20 parts by weight,
and more preferably from 0.5 to 10 parts by weight, based on 100
parts by weight of the binder resin. An amount less than 0.1 part
by weight can not bring about a sufficient releasing effect, and an
amount more than 20 parts by weight tends to result in a lowering
of the blocking resistance of the toner.
The graft-modified polyolefin used in the present invention may
preferably have a melt viscosity of 1 to 250 cps (centipoise) at
160.degree. C. A melt viscosity less than 1 cps tends to cause the
blocking of toner. A melt viscosity more than 250 cps makes it hard
for the modified polyolefin to bleed from the toner and makes it
hard for the releasing effect to be exhibited. In the fixing method
of the present invention, it is preferred that in general a
releasable component having a lower melt viscosity is used when a
lower fixing temperature is selected.
The melt viscosity referred to in the present invention is based on
a value measured with a Brookfield type viscometer.
In the toner of the present invention, in the instance where i) the
polyester resin obtained by co-condensation polymerization of the
etherified bisphenol with the carboxylic acid comprised of a
carboxylic acid with two or more carboxylic groups, an anhydride
thereof or a lower-alkyl ester thereof and the release agent are
contained, ii) the polyester resin has the properties that the melt
viscosity .eta.' measured with an overhead-type flow tester is from
10.sup.3 to 10.sup.6 poise at a temperature within the temperature
range of from 80.degree. C. to 120.degree. C. and an absolute value
of the inclination of a graph is not more than 0.50 ln
(poise)/.degree.C. when the natural logarithms ln.eta. of the melt
viscosity at 80.degree. C. and 120.degree. C. are plotted with
respect to the temperatures and also iii) the release agent is the
polyolefin graft-modified with an aromatic vinyl monomer and an
unsaturated fatty acid or unsaturated fatty acid ester, having a
melt viscosity of 1 to 250 cps (centipoise) at 160.degree. C., and
is contained in an amount of from 0.1 to 20% by weight based on the
total weight of the binder resin;
Other resins may also be contained in the toner in addition to the
polyester resin comprised of the above component materials, in an
amount less than (preferably in an amount of not more than 30% by
weight of) the polyester resin and so as for the melt viscosity
.eta.' measured by an overhead-type flow tester not to deviate from
a value outside the range of from 10.sup.3 to 10.sup.6 poise at a
temperature within the temperature range of from 80.degree. C. to
120.degree. C., and for the absolute value of the inclination of a
graph not to become more than 0.50 ln (poise)/.degree.C. when the
natural logarithms ln.eta.' of the melt viscosity at 80.degree. C.
and 120.degree. C. are plotted with respect to the temperatures.
Such resins include vinyl resins mainly composed of styrene,
styrene-butadiene resins, silicone resins, polyurethane resins,
polyamide resins, epoxy resins, polyvinyl butyral resins, rosin,
modified rosins, terpene resins, phenol resins, aliphatic or
alicyclic hydrocarbon resins, aromatic petroleum resins,
chlorinated paraffin, and paraffin wax.
In the toner according to another embodiment of the present
invention, in the instance where i) the polyester resin having an
acid value of from 5 to 60 comprised of at least;
(A) an etherified bisphenol;
(B) not less than 30 mol % of an aromatic dicarboxylic acid, in all
acid components;
(C) 5 to 40% by weight of an alkenyl-substituted dicarboxylic acid
and/or an alkyl-substituted dicarboxylic acid, based on the total
amount of acids; and
(D) a polycarboxylic acid with three or more carboxylic groups
and/or polyols with three or more hydroxyl groups;
and the organic metal compound containing a metal having a valence
of two or more, used in an amount of from 0.2 to 6% by weight based
on the resin are contained, ii) the coloring component and the
releasable component are also contained, iii) the melt viscosity
.eta.' as a toner, measured by an overhead-type flow tester is from
10.sup.3 to 10.sup.6 poise at a temperature within the temperature
range of from 120.degree. C. to 150.degree. C. and an absolute
value of the inclination of a graph is not more than 0.50 ln
(poise)/.degree.C. when the natural logarithms ln.eta.' of the melt
viscosity at 120.degree. C. and 150.degree. C. are plotted with
respect to the temperatures, and also iv) the releasable component
is the polyolefin graft-modified with an aromatic vinyl monomer and
an unsaturated fatty acid or unsaturated fatty acid ester, having a
melt viscosity of 1 to 250 cps (centipoise) at 160.degree. C., and
is contained in an amount of from 0.1 to 20% by weight based on the
total weight of the binder resin;
Other resins may also be contained in addition to the polyester
resin in an amount less than the amount of polyester resin and so
as for the melt viscosity .eta.' measured by an overhead-type flow
tester not to become outside the range of from 10.sup.3 to 10.sup.6
poise at a temperature within the temperature range of from
120.degree. C. to 150.degree. C., and for the absolute value of the
inclination of a graph not to become more than 0.50 ln
(poise)/.degree.C. when the natural logarithms ln.eta.' of the melt
viscosity at 120.degree. C. and 150.degree. C. are plotted with
respect to the temperatures. Such resins include, for example,
vinyl resins mainly composed of styrene, styrene-butadiene resins,
silicone resins, polyurethane resins, polyamide resins, epoxy
resins, polyvinyl butyral resins, rosin, modified rosins, terpene
resins, phenol resins, aliphatic or alicyclic hydrocarbon resins,
aromatic petroleum resins, chlorinated paraffin, and paraffin
wax.
In instances in which the toner is used as a magnetic toner
containing magnetic fine particles, a material that exhibits
magnetism or can be magnetized is used as the magnetic fine
particles. Such a material includes, for example, metals such as
iron, manganese, nickel, cobalt, and chromium; magnetite, hematite,
all sorts of ferrites, manganese alloys, and other ferromagnetic
alloys. These materials can be used in the form of fine powder
having an average particle diameter of from 0.05 to 5 .mu.m. The
magnetic fine particles may be contained in the magnetic toner
preferably in an amount of from 15 to 70% by weight, and more
preferably from 25 to 45% by weight, based on the total weight of
the magnetic toner.
In the toner used in the present invention, various materials can
be added for the purpose of coloring or electrostatic charge
control. Such materials include, for example, carbon black,
graphite, Nigrosine, metal complexes of monoazo dyes, ultramarine
blue, and all sorts of lake pigments such as Phthalocyanine Blue,
Hansa Yellow, Benzidine Yellow and Quinacridone.
Colloidal silica may also be contained in the toner particles as a
fluidity improver in an amount of from 10 to 40% by weight. This
fluidity improver may be mixed with the toner, in the instance of
which it is added preferably in an amount of from 0.2 to 5% by
weight based on the toner weight.
The toner used in the heat-fixing method of the present invention
may preferably be a toner showing a maximum value of from
40.degree. C. to 120.degree. C., of the endothermic peak T.sub.D
that first appears as a result of the measurement made within the
measurement range of from 10.degree. C. to 200.degree. C. using a
DSC. In particular, more preferred is a toner showing a
characteristic of from 55.degree. C. to 100.degree. C.
The temperature at the time the film is peeled from the toner-fixed
face may preferably be higher than the above endothermic
temperature. More preferably, the film may be peeled under
conditions of at least 30.degree. C. higher, and more preferably be
from 40.degree. to 150.degree. C. higher, than the above
endothermic temperature.
As for the method of measuring the maximum value of the endothermic
peak as used in the present invention, the value can be calculated
according to ASTM D-3418-82. Stated specifically, 10 to 15 mg of
the toner is collected, which is then heated in a nitrogen
atmosphere at a rate of temperature rise of 10.degree. C./min from
room temperature to 200.degree. C., and thereafter the temperature
is maintained at 200.degree. C. for 10 minutes, followed by rapid
cooling. The toner is thus pre-treated. Thereafter, the temperature
is maintained at 10.degree. C. for 10 minutes, and the toner is
again heated to 200.degree. C. at a rate of temperature rise of
10.degree. C./min, where the measurement is made. The data as shown
in FIG. 3 can be commonly obtained, and the maximum value of the
endothermic peak that first appears is defined as the endothermic
temperature (T.sub.D).
In the present invention, the heater element has a smaller heat
capacity than conventional heat rolls, and has a linear heating
part. The heating part may preferably be made to have a maximum
temperature of from 100.degree. to 300.degree. C.
A film is interposed between the heater element and the pressure
member, and may preferably comprise a heat-resistant sheet of from
1 to 100 .mu.m in thickness. Heat-resistant sheets that can be used
therefor include sheets of polymers having high heat-resistance,
such as polyester, polyethylene terephthalate (PET), a
tetrafluoroethylene/ perfluoroalkyl vinyl ether copolymer (PFA),
polytetrafluoroethylene (PTFE), polyimide and polyamide, sheets of
metals such as aluminum, and laminate sheets comprised of a metal
sheet and a polymer sheet.
In a preferred constitution of the film, these heat-resistant
sheets have a release layer and/or a low-resistance layer.
A preferred embodiment of the present invention will be described
below with reference to the accompanying drawings.
FIG. 4A illustrates the structure of the fixing device in the
present embodiment.
In FIG. 4A, the numeral 11 denotes a low heat capacitance linear
heater element stationarily supported in the fixing device. An
example thereof comprises an alumina substrate 12 of 1.0 mm in
thickness, 10 mm in width and 240 mm in longitudinal length and a
resistance material 13 coated thereon with a width of 1.0 mm, which
is electrified from the both ends in the longitudinal direction.
The electricity is applied under variations of pulse widths of the
pulses corresponding with the desired temperatures and energy
emission quantities which are controlled by a temperature sensor
14, in the pulse-like waveform with a period of 20 msec of DC 100
V. The pulse widths range approximately from 0.5 msec to 5 msec. In
contact with the heater element 11 the energy and temperature of
which have been controlled in this way, a fixing film 15 moves in
the direction of the arrow shown in FIG. 4A. An example of this
fixing film includes an endless film comprised of a heat-resistant
sheet of 20 .mu.m thick (comprising, for example, polyimide,
polyetherimide, PES, or PFA) and a release layer (comprising a
fluorine resin such as PTFE or PFA to which a conductive material
is added) coated at least on the side coming into contact with
images to have a thickness of 10 .mu.m. In general, the total
thickness of the film may preferably be not more than 100 .mu.m,
and more preferably less than 40 .mu.m. The film is moved in the
direction of the arrow in a wrinkle-free state by the action of the
drive of, and tension between, a drive roller 16 and a follower
roller 17.
The numeral 18 denotes a pressure roller having on its surface an
elastic layer of rubber with good release properties as exemplified
by silicone rubber. This pressure roller is pressed against the
heater element at a total pressure of 4 to 20 kg through the film
interposed between them and is rotated in pressure contact with the
film. Toner 20 having not been fixed on a transferring medium 19 is
led to the fixing zone by means of an inlet guide 21. A fixed image
is thus obtained by the heating described above.
The above has been described with reference to the endless belt. As
FIG. 4B shows, however, a sheet-feeding shaft 24 and a wind-up
shaft 27 may also be used, where the fixing film may not be
endless.
The image forming apparatus includes an apparatus that forms an
image by the use of a toner, as exemplified by copying machines,
printers, and facsimile apparatus, to which the present fixing
device can be applied.
When the temperature detected by the temperature sensor 14 in the
low heat capacitance linear heater element 11 is T.sub.1, the
surface temperature T.sub.2 of the film 15 opposed to the
resistance material 13 is substantially equal to T.sub.1. The
surface temperature T.sub.3 of the film on the part at which the
film 15 is peeled from the toner-fixed face is a temperature
substantially equal to the above temperatures T1 and T2.
The present invention will be described below in greater detail by
giving Examples and Comparative Examples which contain examples for
preparing polyester resins used therein and examples for preparing
toners that employ the resins as binder resins.
Examples of graft-modified polyolefins used in the examples of the
present invention are shown in the following Table 1.
TABLE 1
__________________________________________________________________________
Release agent (Graft-modified polyolefin) .eta..sup.'(vis- Graft
components cosity) Aromatic Unsaturate at 160.degree. C. Backbone
polymer vinyl monomer fatty acid (ester) (cP)
__________________________________________________________________________
1 Polyethylene (100) Styrene (10) 2-Ethylhexyl acrylate (3) 11 2
Polyethylene (100) Styrene (5) n-Butyl methacrylate (15) 7 3
Polyethylene (100) Styrene (8) Acrylic acid (2) 8 4 Polyethylene
(100) Styrene (20) Butyl acrylate (20) 27 5 Polyethylene (100)
Vinyltoluene (14) n-Butyl methacrylate (14) 15 6
Ethylene/polypropylene (3/97) Styrene (10) 2-Ethylhexyl acrylate
(4) 90 copolymer 7 Ethylene/polypropylene (3/97) Styrene (9)
2-Hydroxyethyl (6) 85 copolymer methacrylate 8
Ethylene/polypropylene (95/5) Styrene (17) Butyl acrylate (13) 17
copolymer 9 Ethylene/polypropylene (95/5) .alpha.-Methyl- (4) Butyl
acrylate (6) 23 copolymer styrene 10 Ethylene/polypropylene (95/5)
Vinyltoluene (11) Diethyl itaconate (13) 33 copolymer 11
Polypropylene (100) Styrene (10) 2-Ethylhexyl acrylate (3) 110 12
Polypropylene (100) Styrene (5) n-Butyl methacrylate (15) 32 13
Polypropylene (100) Styrene (20) Butyl acrylate (20) 43 14
Polypropylene (100) Styrene (9) Dimethylaminoethyl (1) 93
methacrylate 15 Polypropylene (100) Vinyltoluene (7) Dodecyl
methacrylate (7) 82
__________________________________________________________________________
In (): Weight ratio
EXAMPLE 1
______________________________________ Polyoxypropylene 22.0 parts
by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene
32.5 parts by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Fumaric
acid 16.5 parts by weight Terephthalic acid 29 parts by weight
______________________________________
The above materials in a total amount of 1,500 g were put into a 2
lit. volume four-necked round flask equipped with a thermometer, a
stirrer made of stainless steel, a nitrogen-feeding tube made of
glass, and a falling condenser. Subsequently, the flask was placed
in a mantle heater, and nitrogen gas was fed from the feeding tube
made of glass so that the inside of the reaction vessel was made to
keep an inert atmosphere. Temperature was then raised. Thereafter,
0.10 g of dibutyltin oxide was added, the temperature was
maintained at 210.degree. C., and co-condensation reaction was
carried out for 12 hours to give polyester resin A.
This polyester resin A showed an apparent viscosity .eta.a' at
t.sub.a =80.degree. C. and an apparent viscosity .eta.b' at t.sub.b
=120.degree. C. as measured by the overhead-type flow tester shown
in FIG. 1, of 7.9.times.10.sup.5 poise and 8.5.times.10.sup.2
poise, respectively. The absolute value of the inclination of the
natural logarithms ln.eta.' of the melt viscosity with respect to
the temperature was found to be 0.17 ln (poise)/.degree.C.
Using a twin-screw kneader extruder, 100 parts by weight of the
above polyester resin A, 6 parts by weight of a copper
phthalocyanine pigment, 2 parts by weight of a negative charge
control agent and 4 parts by weight of the graft-modified
polyolefin No. 1 as shown in Table 1 were melt-kneaded. Thereafter,
the kneaded product was cooled and then pulverized using an
air-stream pulverizer, followed by classification using an air
classifier to give a blue fine powder (a blue toner) with an
average particle diameter of 12.5 .mu.m. Based on 100 parts by
weight of this blue fine powder, 0.6 part by weight of hydrophobic
colloidal silica powder was added and mixed to give toner A having
hydrophobic silica particles on the toner particle surfaces. This
toner A showed T.sub.D =56.degree. C. Subsequently, based on 8
parts by weight of this toner A, 100 parts by weight of a coating
ferrite carrier (coating agent: a fluorine-acrylate-styrene
copolymer) was mixed to give developer A.
In the heat-fixing device of the present invention, as shown in
FIG. 4A, the temperature sensor surface temperature T.sub.1 of the
heater element 11 was set to 110.degree. C.; the power consumption
of the resistance material at the heating part, 150 W; the total
pressure between the heater element 11 and the pressure roller 18,
5 kg; the nip between the pressure roll and film, 3 mm; and the
rotational speed of the fixing film 15, 50 mm/sec.
As the heat-resistant sheet, a polyimide film of 20 .mu.m thick,
having at the contact face with a recording medium a low-resistance
release layer comprising a conductive material dispersed in PTFE
was used. At this time, it took about 1 second until the
temperature sensor surface temperature T.sub.1 of the heater
element reached 110.degree. C. The temperature T.sub.2 was
108.degree. C., and the temperature T.sub.3 was 107.degree. C.
Evaluation was made in the following way: Using a modified machine
obtained by detaching a fixing device from a commercially available
copying machine NP-6650, manufactured by Canon Inc., the developer
A was put in its developing device for color copying to carry out
image production. Thus, an unfixed image of toner A was obtained.
As a recording medium, commercially available 54 g/m.sup.2 Canon
New Dry Paper (available from Canon Sales, Co., Inc.) for use in
copying machines was used. The resulting unfixed image of toner A
was fixed using the above fixing device to give a fixed image.
For fixing performance tests on the fixed image, unfixed images on
200 sheets were successively papered through the fixing device to
give fixed images, and the 1st, 10th, 50th, 100th and 200th sheets
were each rubbed with Silbon paper under application of a load of
50 g/cm.sup.2. The fixing performance was expressed by the rate (%)
of a lowering of image density. For offset resistance tests, the
entirely solid black unfixed images were successively fixed, and
evaluation was made on how many sheets were papered until the fixed
image or fixing film became stained.
As a result, the fixing performance was almost constant at the
initial stage and the 200th sheet in 200 sheet papering, showing
that it was as good as 0 to 1%. As to the offset resistance, almost
no adhesion of toner on the surfaces of the fixing film 15 and
pressure roller 18 was seen even after 20,000 sheet papering. The
resulting fixed images were free from bleeding or bleed-through and
were in good quality.
Comparative Example 1
A toner was prepared in the same manner as in Example 1 except that
the release agent (the graft-modified polyolefin No. 1) of the
toner A shown in Example 1 was replaced with a polyethylene not
graft-modified (.eta.'=10 cps at 160.degree. C.), and evaluated in
the same manner as in Example 1. As a result, the fixing
performance was 2 to 5% at the initial stage and the 200th sheet in
200 sheet papering. Almost no adhesion of toner on the surfaces of
the fixing film 15 and pressure roller 18 was seen after 10,000
sheet papering, but a little offset was seen on the fixing film 15
after 20,000 sheet papering.
EXAMPLE 2
Toner B prepared in the same manner as in Example 1 except that the
graft-modified polyolefin No. 8 was used as the release agent in
place of the graft-modified polyolefin No. 1 in the toner A was
evaluated in the same manner as in Example 1. As a result, the
fixing performance was almost constant at the initial stage and the
200th sheet in 200 sheet papering, showing that it was as good as 0
to 1%. As to the offset resistance, almost no adhesion of toner on
the surfaces of the fixing film 15 and pressure roller 18 was seen
even after 20,000 sheet papering. The resulting fixed images were
free from bleeding or bleed-through and were in good quality.
EXAMPLE 3
______________________________________ Polyoxypropylene 24.0 parts
by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene
36.0 parts by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Fumaric
acid 40 parts by weight ______________________________________
Polyester resin B was obtained in the same manner as the polyester
resin A described in Example 1 except for using the above
materials. This polyester resin B showed an apparent viscosity
.eta.a' at t.sub.a =80.degree. C. and an apparent viscosity .eta.b'
at t.sub.b =120.degree. C. as measured by the overhead-type flow
tester shown in FIG. 1, of 4.0.times.10.sup.5 poise and
2.2.times.10.sup.2 poise, respectively. The absolute value of the
inclination of the natural logarithms ln.eta.' of the melt
viscosity with respect to the temperature was found to be 0.19 ln
(poise)/.degree.C.
Toner C was obtained in the same manner as in Example 1 except that
the polyester resin A was replaced with the polyester resin B, and
the graft-modified polyolefin No. 9 was used as the release agent
in place of the graft-modified polyolefin No. 1. The resulting
toner C showed T.sub.D =55.degree. C.
Fixing performance tests and offset resistance tests were carried
out in the same manner as in Example 1 except that the temperature
sensor surface temperature T.sub.1 of the heater element 11 was set
to 150.degree. C.; and the rotational speed of the fixing film 15,
150 mm/sec. As a result, the fixing performance was as good as 1 to
3%. As to the offset resistance, almost no adhesion of toner on the
surfaces of the fixing film and pressure roller was seen even after
20,000 sheet papering.
The waiting time of the fixing device was about 1 second, which was
the same as in Example 1. At this time, the temperature T.sub.2 was
148.degree. C. and the temperature T.sub.3 was 146.degree. C.
The resulting fixed images were free from bleeding or bleed-through
and were in good quality.
EXAMPLE 4
______________________________________ Polyester resin B 100 parts
by weight Magnetic powder 50 parts by weight Negative charge
control agent 2 parts by weight Graft-modified polyolefin No. 5 4
parts by weight ______________________________________
Using a twin-screw kneader extruder, the above materials were
melt-kneaded. Thereafter, the kneaded product was cooled and then
pulverized using an air-stream pulverizer, followed by
classification using an air classifier to give a black fine powder
(a magnetic toner) with an average particle diameter of 12.0 .mu.m.
Based on 100 parts by weight of this magnetic toner, 0.4 part by
weight of hydrophobic silica powder was added and mixed to give
toner D having hydrophobic silica particles on the toner particle
surfaces. This toner D showed T.sub.D =57.degree. C.
Using a modified machine obtained by detaching a fixing device from
a commercially available copying machine NP-6650, manufactured by
Canon Inc., the toner D was put in its developing device for black
copying to carry out image production. Thus, an unfixed image of
toner D was obtained. The unfixed image was fixed and the fixed
image was evaluated under the same conditions as in Example 3. As a
result, the fixing performance was as good as 2 to 4%. As to the
offset resistance, almost no adhesion of toner on the surfaces of
the fixing film and pressure roller was seen even after 20,000
sheet papering.
As described above, the present heat fixable toner and the heat
fixing method that employs the toner can achieve good fixing of a
toner image to a recording medium, does not cause the offset
phenomenon on the fixing film, can be free from bleeding or
bleed-through of toner into a recording medium to obtain a
bleeding-free sharp image, and also can lower power consumption and
make the waiting time very short.
Preparation example of polyester resin C:
______________________________________ Polyoxypropylene 24.2 parts
by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene
33.0 parts by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane
Terephthalic acid 20.1 parts by weight n-Dodecenylsuccinic acid 9.7
parts by weight Pyromellitic acid 13.0 parts by weight
______________________________________
The above materials in a total amount of 1,500 g were put into a 2
lit. volume four-necked round flask equipped with a thermometer, a
stirrer made of stainless steel, a nitrogen-feeding tube made of
glass, and a falling condenser. Subsequently, the flask was placed
in a mantle heater, and nitrogen gas was fed from the feeding tube
made of glass so that the inside of the reaction vessel was made to
keep an inert atmosphere. Temperature was then raised. Thereafter,
0.10 g of dibutyltin oxide was added, the temperature was
maintained at 210.degree. C., and co-condensation reaction was
carried out for 12 hours to give polyester resin C. This polyester
resin C had an acid value of 12.0.
Preparation example of toner E:
Using a twin-screw kneader extruder, 100 parts by weight of the
above polyester resin C, 60 parts by weight of magnetic powder
(magnetic iron oxide), 1 part by weight of an organic metal complex
(a chromium complex of 3,5-di-tert-butylsalicylic acid) and 4 parts
by weight of the release agent No. 1 as shown in Table 1 were
melt-kneaded (kneading temperature: 140.degree. C.). Thereafter,
the kneaded product was cooled and then pulverized using an
air-stream pulverizer, followed by classification using an air
classifier to give a magnetic toner with an average particle
diameter of about 12 .mu.m.
A product obtained by molding 15 g of the resulting magnetic toner
by the use of a pressure molding device showed an apparent
viscosity .eta.a' at t.sub.a =120.degree. C. and an apparent
viscosity .eta.b' at t.sub.b =150.degree. C. as measured by the
overhead-type flow tester shown in FIG. 1, of 1.times.10.sup.5
poise and 6.times.10.sup.3 poise, respectively. The absolute value
of the inclination of the natural logarithms ln.eta.' of this
apparent viscosity with respect to the temperature was found to be
0.09 ln (poise)/.degree.C.
Subsequently, based on 100 parts by weight of this magnetic toner,
0.4 part by weight of hydrophobic silica powder was added and mixed
to give toner E having hydrophobic silica particles on the toner
particle surfaces. This toner E showed T.sub.D =65.degree. C.
Preparation example of toner F:
Toner F was obtained in the same manner as the toner E except that
the release agent No. 1 of the toner E was replaced with the
release agent No. 6 shown in Table 1.
The toner F showed substantially the same melt viscosity
characteristics as those of the toner E.
EXAMPLE 5
In the heat-fixing device of the present invention, as shown in
FIG. 4A, the temperature sensor surface temperature T.sub.1 of the
heater element 11 was set to 220.degree. C.; the power consumption
of the resistance material at the heating part, 150 W; the total
pressure between the heater element 11 and the pressure roller 18,
13 kg; the nip between the pressure roll and film, 3 mm; and the
rotational speed of the fixing film 15, 120 mm/sec.
As the heat-resistant sheet, a polyimide film of 20 .mu.m thick,
having at the contact face with a recording medium a low-resistance
release layer comprising a conductive material dispersed in PTFE
was used. At this time, it took about 3 seconds until the
temperature sensor surface temperature T.sub.1 of the heater
element reached 185.degree. C. The temperature T.sub.2 was
183.degree. C., and the temperature T.sub.3 was 182.degree. C.
Evaluation was made in the following way: Using a modified machine
obtained by detaching a fixing device from a commercially available
copying machine NP-270RE, manufactured by Canon Inc., an unfixed
image of toner E was obtained. As a recording medium, commercially
available 54 g/m.sup.2 Canon New Dry Paper (available from Canon
Sales, Co., Inc.) for use in copying machines was used. The
resulting unfixed image of toner E was fixed using the above fixing
device to give a fixed image.
For fixing performance tests on the fixed image, unfixed images on
200 sheets were successively papered through the fixing device to
give fixed images, and the 1st, 10th, 50th, 100th and 200th sheets
were each rubbed with Silbon paper under application of a load of
50 g/cm.sup.2. The fixing performance was expressed by the rate (%)
of a lowering of image density. For offset resistance tests, the
unfixed images were successively fixed, and evaluation was made on
how many sheets were papered until the fixed image or fixing film
became stained.
As a result, the fixing performance was almost constant at the
initial stage and the 200th sheet in 200 sheet papering, showing
that it was as good as 1 to 3%. As to the offset resistance, almost
no adhesion of toner on the surfaces of the fixing film 15 and
pressure roller 18 was seen even after 20,000 sheet papering. The
resulting fixed images were free from bleeding or bleed-through and
were in good quality.
EXAMPLE 6
Using the toner F, fixing performance tests were carried out in the
same manner as in Example 5. As a result, like the toner E, the
toner F showed superior fixing performance and offset
resistance.
Preparation example of polyester resin D:
______________________________________ Polyoxypropylene 29.5 parts
by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene
34.5 parts by weight (2,2)-2,2-bis(4-hydroxyphenyl)propane
Terephthalic acid 22.0 parts by weight n-Dodecenylsuccinic acid 8.3
parts by weight Pyromellitic acid 5.7 parts by weight
______________________________________
Polyester resin D was obtained in the same manner as the polyester
resin C except for using the above materials. The resulting
polyester resin D had an acid value of 21.5.
Preparation example of toner G:
Using a twin-screw kneader extruder, 100 parts by weight of the
above polyester resin D, 4 parts by weight of the release agent No.
7 as shown in Table 1, 60 parts by weight of magnetic powder
(magnetic iron oxide) and 0.5 part by weight of an organic metal
compound (an acetylacetone iron) were melt-kneaded (kneading
temperature: 140.degree. C.). Thereafter, the kneaded product was
cooled and then pulverized using an air-stream pulverizer, followed
by classification using an air classifier to give a magnetic toner
with an average particle diameter of about 12 .mu.m.
A product obtained by molding 15 g of the resulting magnetic toner
by the use of a pressure molding device showed an apparent
viscosity .eta.a' at t.sub.a =120.degree. C. and an apparent
viscosity .eta.b' at t.sub.b =150.degree. C. as measured by the
overhead-type flow tester shown in FIG. 1, of 6.0.times.10.sup.4
poise and 1.2.times.10.sup.3 poise, respectively. The absolute
value of the inclination of the natural logarithms ln.eta.' of this
apparent viscosity with respect to the temperature was found to be
0.13 ln (poise)/.degree.C.
Subsequently, based on 100 parts by weight of this magnetic toner,
0.4 part by weight of hydrophobic silica powder was added and mixed
to give toner G having hydrophobic silica particles on the toner
particle surfaces. This toner G showed T.sub.D =73.degree. C.
Preparation example of toner H:
Toner H was obtained in the same manner as the toner G except that
the release agent No. 7 of the toner G was replaced with the
release agent No. 11 shown in Table 1.
EXAMPLE 7
Fixing performance tests and offset resistance tests were carried
out using the toner G, in the same manner as in Example 5 except
that the temperature sensor surface temperature T.sub.1 of the
heater element 11 was set to 190.degree. C.; and the rotational
speed of the fixing film 15, 150 mm/sec. As a result, the fixing
performance was as good as 1 to 3%. As to the offset resistance
also, good results were seen up to 20,000 sheet papering.
The waiting time of the fixing device was about 3 second, which was
the same as in Example 5. At this time, the temperature T.sub.2 was
188.degree. C. and the temperature T.sub.3 was 187.degree. C.
The resulting fixed images were free from bleeding or bleed-through
and were in good quality.
EXAMPLE 8
Using the toner H in place of the toner G, fixing performance tests
were carried out in the same manner as in Example 7. As a result,
like the toner G, the toner H showed superior fixing performance
and offset resistance.
Preparation of comparative toner I:
In the same manner as in the case of the toner E, 100 parts by
weight of the polyester resin C, 60 parts by weight of magnetic
powder (magnetic iron oxide), 1 part by weight of an organic metal
complex (a chromium complex of 3,5-di-tert-butylsalicylic acid) and
4 parts by weight of an unmodified polyethylene wax were
melt-kneaded. The kneaded product was pulverized and then
classified to give a comparative toner I. The comparative toner I
had the same melt viscosity as the toner E.
Comparative Example 2
Fixing performance tests were carried out using the toner I in
place of the toner E. As a result, the fixing performance was
almost constant at the initial stage and the 200th sheet in 200
sheet papering, showing that it was 3 to 5%, which was a little
poorer result than in the toner E (Example 5). As to the offset
resistance, the same results were seen in 10,000 sheet papering,
but adhesion of toner on the surfaces of the pressure roller and
fixing film occurred after 20,000 sheet papering.
Preparation Example 1
______________________________________ Polyoxypropylene 60 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Fumaric acid 40 mol %
______________________________________
To the above materials, dibutyltin oxide was added in an amount of
0.05 mol % based on the total acid components. The system was kept
at 210.degree. C. While a stirring blade was rotated, the system
was evacuated to 5 mmHg after 4 hours at the time when the
effluence of the water in the system stopped. As a result, with the
distillation of dialcohol components, the rotational load of the
stirring blade gradually increased, and the load began to abruptly
increase after 1.5 hours. Here the pressure inside the system was
changed to 50 mmHg, so that the increase in stirring load became
slow. This operation was repeated several times until the pressure
inside the system came to be 300 mmHg, so that the distilling
components came to be little produced. At this stage, the pressure
inside the system was returned to ordinary pressure, and the
stirring was continued for about 1 hour, followed by cooling to a
room temperature to give linear polyester resin E having an acid
value of 3.
Preparation Example 2
______________________________________ Polyoxypropylene 35 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Ethylene glycol 20 mol %
Terephthalic acid 25 mol % Isophthalic acid 20 mol %
______________________________________
From the above monomers, linear polyester resin F having an acid
value of 2 was obtained in the same manner as in Preparation
Example 1.
Preparation Example 3
______________________________________ Propylene glycol 30 mol %
Ethylene glycol 30 mol % Terephthalic acid 25 mol % Triethylene
dicarboxylic acid 15 mol %
______________________________________
From the above monomers, linear polyester resin G having an acid
value of 3 was obtained in the same manner as in Preparation
Example 1.
Preparation Example 4
Using the same monomers as in Preparation Example 1, linear
polyester resin H having an acid value of 15 was obtained in the
same manner as in Preparation Example 1 except that the pressure
inside the system was not controlled.
Preparation Example 5
______________________________________ Polyoxypropylene 45 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Fumaric acid 45 mol %
Trimellitic acid 10 mol %
______________________________________
From the above monomers, non-linear polyester resin I having an
acid value of 35 was obtained in the same manner as in Preparation
Example 4.
Preparation Example 6
______________________________________ Polyoxypropylene 30 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene 21 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Terephthalic acid 23 mol %
Succinic acid substituted with a C.sub.12 20 mol % alkyl group
Trimellitic acid 6 mol % ______________________________________
From the above monomers, non-linear polyester resin J having an
acid value of 40 was obtained in the same manner as in Preparation
Example 4.
Preparation Example 7
______________________________________ Polyoxypropylene 10 mol %
(2,5)-2,2-bis(4-hydroxyphenyl)propane Polyoxyethylene 5 mol %
(2,2)-2,2-bis(4-hydroxyphenyl)propane Triethylene glycol 35 mol %
Terephthalic acid 25 mol % Isophthalic acid 19 mol % Trimellitic
acid 6 mol % ______________________________________
From the above monomers, non-linear polyester resin K having an
acid value of 40 was obtained in the same manner as in Preparation
Example 4.
Preparation Example 8
The monomers used in Preparation Example 5 were polymerized by the
method used in Preparation Example 1 to give non-linear polyester
resin L having an acid value of 3.
Preparation Example 9
Non-linear polyester resin M was obtained in entirely the same
manner as in Preparation Example 5 except that the reaction was
stopped at the time when the acid value reached 70.
Fixing
A fixing unit of a copying machine FC-5, manufactured by Canon
Inc., was taken out and so modified as to have a pressure between
upper and lower rolls, of 0.30 kg/cm in linear pressure, a nip
width of 3.0 mm, a linear velocity of 60 mm/sec, an upper roll
temperature made variable between 100.degree. C. and 270.degree. C.
Modified fixing device I was thus made ready for use. In the same
way, modified fixing device II (pressure between upper and lower
rolls: 2.5 kg/cm; nip width: 6.0 mm; linear velocity: 450 mm/sec;
upper roll temperature: made variable between 100.degree. C. and
270.degree. C.) of a copying machine NP-7550, manufactured by Canon
Inc., was also made ready for use. Fixing device III as shown in
FIG. 4A was also made ready for use.
Development performance
Using a copying machine NP-4835, manufactured by Canon Inc., in the
case of positively chargeable toner and a modified copying machine
of NP-4835 in the case of negatively chargeable toner, a continuous
100,000 sheet copying test was carried out. In the case of
non-magnetic toners, the ratio T/c, the ratio of a toner to a
carrier, was set to be 8/100. The carrier used was comprised of a
ferrite core coated with a styrene/methyl methacrylate/fluorine
copolymer.
Blocking
Toners were left to stand for 3 days in an atmosphere of 50.degree.
C., and the state of blocking was visually observed.
EXAMPLE 9
______________________________________ Polyester resin E 70 parts*
Polyester resin I 30 parts Iron (II) acetylacetonate 1 part
Magnetic material 70 parts Nigrosine dye 2 parts
______________________________________ *by weight (the same applies
hereinafter)
In the above materials, 4 parts of a graft-modified polyolefin
release agent W1 comprised of styrene and butyl acrylate used as
graft components and having a number average molecular weight Mn of
5.3.times.10.sup.2, a weight average molecular weight Mw of
8.0.times.10.sup.2, an Mw/Mn of 1.5 and a melting point of
93.degree. C. was mixed. The mixture was melt-kneaded using a
twin-screw kneader extruder. Thereafter, the kneaded product was
cooled and then pulverized, followed by classification to give a
magnetic toner with a weight average particle diameter of 11 .mu.m.
Subsequently, 100 parts of this magnetic toner and 0.4 part of
amino-modified silicone oil treated silica fine powder were mixed
to give a positively chargeable magnetic toner.
The fixing performance was evaluated using the fixing device I.
Fixing point was 125.degree. C. High-temperature offset occurred at
200.degree. C. or higher. The temperature region in which the
fixing can be performed was 85.degree. C. These were very superior
results.
With regard to development performance, image density of from 1.35
to 1.38 was retained, and fog-free images were stably obtained.
There was no problem in respect of blocking.
Examples 10 to 13, & Comparative Examples 3 to 5
Formulation of toners is summarized in Table 2, and results of
evaluation, in Table 3.
As the graft-modified polyolefin release agent, a graft-modified
polyethylene release agent W2 modified with styrene, butylene
acrylate (Mn=4.5.times.10.sup.2, Mw=5.9.times.10.sup.2, Mw/Mn=1.3,
melting point=80.degree. C.) and a comparative polyethylene release
agent W3 not graft-modified (Mn=6.0.times.10.sup.2,
Mw=1.4.times.10.sup.3, Mw/Mn=2.3, melting point=118.degree. C.)
were used in addition to the release agent W1 used in Example
9.
In Comparative Example 6, a polyester resin O was used, which was
obtained by adding 4 parts of chromium salicylate to 100 parts of
the polyester resin K, which were melt-kneaded using a twin-screw
kneader extruder, followed by cooling and pulverization.
TABLE 2
__________________________________________________________________________
Charge Re- Magnetic control lease Fluidity (1) (2) Organic metal
compound material agent agent improver (3) parts part(s)*1 parts*1
parts*1 parts*1 parts*2 .mu.m
__________________________________________________________________________
Example: 9 E I Iron(II) acetylacetonate Magnetite Nigrosine dye W1
AMSO silica 11.0 70 30 1 70 2 4 0.4 10 F J Iron(II) acetylacetonate
Magnetite Nigrosine dye W2 AMSO silica 8.0 80 20 1 80 2 4 0.6 11 G
K Chromium salicylate Magnetite None W2 HPC silica 10.5 75 25 1 70
4 0.5 12 E J Iron(II) acetylacetonate None Nigrosine dye W1 AMSO
silica 11.0 60 40 1.5 2 4 1.0 13 F I Chromium salicylate None None
W1 HPC silica 8.0 70 30 1 4 0.5 Comparative Example: 3 H J Iron(II)
acetylacetonate Magnetite Nigrosine dye W2 AMSO silica 8.0 80 20 1
80 2 4 0.6 4 E L Iron(II) acetylacetonate Magnetite Nigrosine dye
W1 AMSO silica 11.0 70 30 1 70 2 4 0.4 5 E J Iron(II)
acetylacetonate None Nigrosine dye W3 AMSO silica 11.0 60 40 1.5 2
4 1.0
__________________________________________________________________________
(1): Linear polyester resin, (2): Nonlinear polyester resin (3):
Average particle diameter of toner AMSO silica: Aminomodified
silicone oil treated silica HPC silica: Hydrophobic colloidal
silica *1: based on 100 parts of binder resin *2: based on 100
parts of toner
TABLE 3 ______________________________________ Fixing Developing
point (2) (3) performance, Block- (1) .degree.C. .degree.C.
.degree.C. density/fog ing ______________________________________
Example: 9 I 125 200 75 1.35 to 1.38* None 10 II 140 235 95 1.35 to
1.38* None 11 III 120 220 100 1.34 to 1.36* None 12 I 120 210 90
1.35 to 1.38* None 13 III 125 205 80 1.34 to 1.36* None Comparative
Example: 3 II 160 205 45 1.35 to 1.38* None 4 I 120 160 40 1.35 to
1.38* None 5 I 135 205 70 1.35 to 1.38* Occur- ed
______________________________________ (1): Fixing device used in
evaluation (2): Temperature at which hightemperature offset
occurred (3): Fixable temperature region *No fog occurred.
As having been described above, the toner of the present invention
can provide an image having a superior low-temperature fixing
performance and a high quality. In addition, it can promise a high
production efficiency, and can be stably supplied.
* * * * *